18,797 reputation
14098
bio website lightandmatter.com
location Fullerton, California
age
visits member for 3 years
seen 2 days ago

I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


Oct
21
comment Time dilation only on electromagnetic force?
@Nicolas: Only the weak force has been unified with electromagnetism. If you choose a nucleus that alpha decays, then your radioactive clock is purely based on the strong nuclear force.
Oct
21
answered Expansion of the Universe: Conversion of gravitational potential energy to kinetic energy?
Oct
21
comment Victorian cosmology after the second law of thermodynamics but before relativity?
@AlanSE: I agree that there was a lack of knowledge on certain points such as the nucleus, and that it's not reasonable to blame them for not reaching certain specific conclusions that might seem obvious now. However, I still think it's interesting to figure out what they might conceivably have inferred, if they hadn't gone down various wrong paths. Proposing that it could burn out seems like a jump they didn't have the background to make. Kelvin did propose that it would burn out. He just got the time wrong because he thought the source of the sun's energy was gravitational PE.
Oct
21
comment How do you prove the second law of thermodynamics from statistical mechanics?
Interesting. Do you know where the argument is presented in some place that doesn't have a paywall? I would be interested in seeing what the excluded set of initial conditions looks like. I suppose one could also exclude an identical set of final conditions, in which case one would obtain the inverse of the 2nd law (entropy always decreasing).
Oct
21
comment How do you prove the second law of thermodynamics from statistical mechanics?
@WetSavannaAnimalakaRodVance: Which reminds me, do you have any material on the second law at Light and Matter? Here you go: lightandmatter.com/html_books/0sn/ch05/ch05.html
Oct
21
comment How do you prove the second law of thermodynamics from statistical mechanics?
@joshphysics: I'm confident you won't find any such proof, since none has been found in the 160 years since the 2nd law was first formalized, and Loschmidt's argument explains why. No-go theorems may be unreliable in some cases, but one that has stood the test of time for 160 years looks pretty reliable to me.
Oct
21
awarded  Necromancer
Oct
21
comment Why can we skate on ice?
If you have access to the Colbeck paper, could you give us a sketch of what it says, and/or what your own calculations say?
Oct
20
comment Why can we skate on ice?
Some references: ncbi.nlm.nih.gov/pubmed/1517252 , scitation.aip.org/content/aapt/journal/ajp/63/10/10.1119/… . Unfortunately these are both paywalled.
Oct
20
comment Why rendezvous attempt failed on Gemini 4?
One way to check the validity of the tidal explanation would be to verify that the effect of the forces being discussed on a cloud of test particles is to distort the cloud without changing its volume. Another way might be to see if the effect scales like $r^{-3}$.
Oct
20
comment Are quantum decoherence and Everettian approaches to the measurement problem necessarily distinct?
I'm not saying that distinctness has to be defined by empirical testing. But if you're not defining it that way, then it's not clear that your question has a specific answer unless you clarify how you are defining it.
Oct
20
awarded  Electorate
Oct
20
revised counting refractive index of a plano convex lens
fix spelling
Oct
20
comment Why is the wave function complex?
Why the downvotes?
Oct
20
comment Are quantum decoherence and Everettian approaches to the measurement problem necessarily distinct?
A nontrivial issue here is what would qualify as "distinct." Usually we consider two scientific theories to be distinct if they make different predictions about the outcomes of experiments. By this criterion, for example, the Schrodinger wave picture and Heisenberg matrix picture are not distinct; they are different mathematical representations of the same underlying theory. But no interpretation of QM ever makes a prediction about the outcome of any experiment that differs from the predictions made by other interpretations.
Oct
20
comment Can a free particle absorb/emit photons?
Note that if the particle has internal structure, this argument can fail. For example, atomic nuclei emit gamma rays. This is because they have more than one internal state with different energies.
Oct
20
comment How do you prove the second law of thermodynamics from statistical mechanics?
@Trimok: I added a link to a different answer in which I spelled out some of the stuff you're asking about.
Oct
20
revised How do you prove the second law of thermodynamics from statistical mechanics?
added 359 characters in body
Oct
20
comment Is a world with constant/decreasing entropy theoretically impossible?
related: physics.stackexchange.com/q/81465
Oct
20
comment How do you prove the second law of thermodynamics from statistical mechanics?
This is nearly a duplicate of this question: physics.stackexchange.com/q/20401